Check valves are quite common in fluid devices, such as in piston type pumps where back flow is to be checked during a return stroke. One type of valve is a ball valve comprising a ball that is held in a retaining device and is forced against a seat to close off flow when there is a back pressure. These are simple in concept but there are problems with components and construction of valves for some applications. One such problem area is in pumps for liquid chromatography, where there is a combination of requirements for small size, high pressure, corrosive liquids and low cost, with a well controlled ball travel to provide small reverse flow to seal the ball.
Objects of the invention are to provide an improved check valve assembly useful for high pressure corrosive fluids, to provide such a valve assembly that is small in size, to provide such a valve assembly that can withstand very high fluid pressure, to provide such a valve assembly having a relatively few number of parts, and to provide such a valve assembly at relatively low cost.